This invention applies to a category of self-propelled, climbing, mobile platforms that make use of endless tracks to connect to the climbing surface. For this purpose, the term climbing mobile platform refers to a vehicle that is capable of traversing a surface horizontally or vertically in some inclined position relative to the earth horizon. Further, it is intended that the mobile platforms are able to accommodate irregularity in the climbing surface including convex or concave regions. Such platforms may be used to conduct remote operations such as inspection, maintenance, or manufacturing in environments that pose difficulty or danger for human operation. These systems could be used in a wide variety of applications including power production, civil structures, or shipbuilding. A variety of climbing mobile platforms have been proposed to operate in these conditions.
The methods of achieving mobility for climbing platforms include but are not limited to legged locomotion, wheeled devices or endless tracks. The use of endless tracks in climbing platforms provides several advantages, including the potential for a large area of contact between the climbing surface and climbing vehicle. The large area of contact allows for a large distribution of adhering elements such as magnets, suction cups, adhesive, or other device. The endless track-type climbing vehicles presented in previous technologies make use of an endless track that makes contact with the climbing surface over a portion of the track, called here the contact portion of the track. The endless track contains the specific property that it has very high stiffness along the longitudinal axis of the track, but negligible stiffness in all transverse directions and negligible stiffness in bending or torsion. This creates a technical disadvantage in that the endless track is only able to transmit any significant level of forces in a direction along the longitudinal axis of the track. This property also allows the endless track to easily deflect in transverse directions or bend to accommodate irregular climbing surfaces. The result of this high longitudinal stiffness and negligible transverse or bending stiffness is that the endless track is only able to transfer forces normal to the climbing surface at the end portions of the contact region. These forces generally consist of those required to keep the climbing platform in equilibrium and in contact with the climbing surface. Thus, the adhering elements located at each end of the contact region support the majority of the climbing forces.
The performance of an endless-track type climbing platform depends on the ability to transfer forces from the collection of adhering members attached to the track, through the endless track to the platform body. There are a number of technologies that address how these forces are transferred from the endless track to the climbing platform body, and to a smaller degree how these forces are distributed to the collection of adhering members. The mechanism for doing this will be called the suspension system. The invention of this patent provides a novel means to distribute the climbing forces in an optimal manner over all adhering track elements while applying a positive surface normal force on the leading adhering member to ensure that it makes contact with surface when climbing.
The prior art considering tracked climbing vehicles with attached adhering members shows either systems without a suspension, or those with a suspension system designed for secondary purposes (for example, track removal from the climbing surface) rather than to distribute loads among the adhering members. Examples of the related prior art are provided as follows.
U.S. Pat. Nos. 5,435,405, 5,884,642, and Shen and Shen, 2005 show climbing vehicles with adhering members attached to an endless track without a suspension or no consideration given to the suspension. This causes the climbing forces to be transferred to the adhering members through the track and thus concentrates the climbing forces on the adhering members located at the ends of the contract region of the endless track.
U.S. Pat. Nos. 5,894,901 and 4,789,037 show climbing vehicles with adhering members attached to an endless track with press devices to push certain regions of the track into the climbing surface, in particular the leading edge of the track when traveling vertically up. However, these devices do not allow for the vehicle to pull on interior portions of the track in the direction of the surface normal and thus cannot distribute the climbing forces over the endless track.
U.S. Pat. No. 4,828,059 shows a climbing vehicle with adhering members attached to an endless track with a track guide that is used to engage and disengage the adhering members from the climbing surface. During operation, the track guide is not engaged and thus behaves as an endless track system that transfers climbing forces to the adhering members through the track.
U.S. Pat. No. 5,487,440 shows a climbing vehicle with adhering members attached to an endless track with a track guide rigidly attached to the vehicle chassis. This both limits the ability of the endless track to conform to the climbing surface and localizes the climbing loads to a small number of adhering members when traveling over any type of surface irregularity.
Xu and Ma (2002) shows an endless-track type climbing vehicle with type of climbing vehicle with magnets called magnetic suckers. A load distribution mechanism is presented as a three link member connected to the vehicle body with a single spring. The article does not show how the endless track would connect with the load scatter mechanism or how forces are transferred from the track to the mechanism. Further, as presented, the load scatter mechanism localizes moment-balance forces to the leading portion of the load scatter mechanism and similarly the leading edge of the endless track.
This patent most closely relates to a 2010 patent application by Canfield and Beard which demonstrates a climbing platform with endless tracks, adhering members attached directly to the endless tracks, with a compliant beam suspension system that connects the endless tracks to the platform chassis. The compliant beam mechanism allows the suspension to simultaneously adapt to irregularities in the climbing surface, while a collection of springs attached to the compliant beam provide the means to distribute forces among all the adhering members. This invention is unique in that it both distributes surface-normal climbing forces among all the adhering members and provides a force on the adhering member at the end of the contact region to ensure that the adhering member makes contact with the climbing surface.
This patent differs from the 2010 patent application by Canfield and Beard in two significant ways. First, the compliant beam portion of the compliant beam suspension apparatus must provide low rotational stiffness and large rotational deflection about the axis transverse to the axis of the endless track and lying in a plane tangent to the climbing surface at each point along the beam and high rotational stiffness in other directions. For most readily available engineering materials, the elastic modulus permits strains of approximately 2% before plastic deformation occurs. In some special cases, this allowable strain rate may be as high as 6% (for example nickel-titanium type alloys called super-elastic materials). When considering a climbing surface, irregularities in the surface can be defined by the radius of curvature. In order to accommodate large variations in the climbing wall, the suspension must match the curvature of the surface irregularities. This induces strain in the compliant beam suspension proportional to the curvature, and will exceed allowable strain levels for any typical climbing terrain. The second limitation is that lateral forces along the axis transverse to the axis of the endless track and lying in a plane tangent to the climbing surface at each point along the beam are large, and must be transferred through the compliant beam to the platform chassis at the endpoints.